* Polished with a Magic Eraser then with toothpaste and water.
* Waxed with Mother's Carnauba Cleaner Wax. I had an old bottle lying around.
All done by hand. Took around 15 minutes.
A couple folks on r/mk have tried using acetone vapor, which can yield even better results. However, if you use acetone vapor too long, your keys will melt. And "how long" isn't an exact science.